1. Field of the Invention
The present invention relates broadly to inter-axle differential assemblies and, more particularly, to a dedicated lubrication pump for an inter-axle differential assembly.
2. Description of the Prior Art
Motor vehicles with solidly connected multiple drive axles are commonly equipped with an inter-axle differential assembly, commonly arranged in a vehicular transmission transfer case or tandem axle power divider to allow torque balance between the drive axles during the vehicle cornering, to compensate for tire size differences, etc., i.e. when there is any physical requirement for speed difference between the drive axles. The inter-axle differential assemblies are widely employed for tandem drive axles of heavy-duty trucks for on- and off-road service as a power divider.
These motor vehicles are, on occasion, driven in situations where there may be unequal traction conditions between the tires of the different drive axles. If the traction condition at any tire falls below that required for sufficient traction effort, high-speed inter-axle differential conditions may occur. These high-speed differential conditions may be potentially severely damaging to critical differential assembly components, such as shaft bearing surfaces as well as rolling contact surfaces of the differential assembly, due to lack of lubrication.
In such drive axles it is common to have a supply of lubricant in a transfer case or axle housing and to provide positive lubricant pressure to the input and output shaft journals and the inter-axle differential that are disposed above the level of lubricant in the housing to prevent damaging the differential gear components during these high speed differential conditions. However, current lubrication pumps for differential assemblies are driven continuously while the vehicle is in motion, although lubrication supply is only needed during occasional conditions of relatively high-speed levels of differential action as it is well known to those skilled in the art. The continuously driven lubrication pump operates and consumes engine power irrespective of the amount of lubrication needed by the shaft journals and other components of the inter-axle differential, thus causing unnecessary parasitic losses in a vehicle power transmission and increasing fuel consumption.
Thus it has been desired to provide a low-cost and convenient way to incorporate a lubricant pump for providing positive flow of lubricant to the shaft journals and the inter-axle differential assembly only as required.